The outgoing line from the low-voltage end of the transformer is 0. 4kV to the distribution cabinet (primary distribution cabinet), then the outgoing line is led to the distribution box (secondary distribution box) in each building, and finally the outgoing line is led to the distribution cabinet. With secondary selective service, each distribution transformer must be able to supply the entire load for maximum reliability benefits. Typically, primary distribution does not directly supply power to devices, secondary distribution.